What To Consider With a Septic Tank Installation

If you are not fortunate to be able to connect to the mains sewage system you will need to consider other means of disposing of sewage waste from your premises.  The most common of these is to use a septic tank system. 

A septic tank has in the past been a large rectangular structure made of brick, stone, concrete or steel buried underground. More modern systems come in the form of a bottle-shaped plastic tank.  A septic tank is a completely passive system powered entirely by gravity.

The size of the septic tank that you will require is determined by factors such as how many bedrooms in a home and the rate at which water flows through the soil on the property.  You should consider future expansion needs, as a septic tank system cannot work efficiently if it is overloaded.

Wastewater flows into the tank at one end. Waste material is allowed to settle in the tank and is digested by natural bacteria, which must be allowed to breed within the tank.  As new water enters the tank, it displaces the water that's already in there. This treated effluent drains from the tank's outlet pipe, normally to a soakaway field drainage system.

Over time partially decomposed solids build up on the bottom of the septic tank. This sludge has to be removed at regular intervals to make sure the tank continues to work properly and to prevent the soakaway becoming clogged.  Cleaning should normally take place every year. 

A septic tank may be considered full when 35 percent of the interior space is occupied by solid material, or sludge.  The tank will always be full of water, which is what you will see if you open the tank.  The solid materials gather at the bottom of the tank and settle there as sludge.  Eventually, this sludge must be pumped out. If the tank is allowed to fill above 35 percent, there is a risk of solid waste entering the pipes to the drainage field or clogging of the inlet to the tank.  Both of these (scenarios|situations} can result in major problems and costly repairs.

Contrary to what many believe, there is no "rule of thumb" for how often septic tanks should be emptied.  For example, an older system with an undersized tank that is being used by a large family will require much more frequent pumping than a new system used by only a few people.  The general advice is that septic tanks should be emptied or de-sludged once per year by an operator licensed for the carriage of waste.

Septic tanks rely on a biological eco system to operate effectively. It is very important that this process is not disrupted.  You should avoid allowing fat, oil, chemicals, solvents or very strong detergents to go into the system. All active ingredients in modern soap and detergents should be biodegradable and, in normal use, should be safe for septic tanks.

The final part of a septic tank system is the soakaway.  Soakaways are relatively simple structures used as part of a drainage system, returning waste water to ground after it has been stored and treated to let bacteria breed and break down pollutants and solid elements.

Septic tank soakaways may be constructed using trenches filled with sand or gravel, through which the waste is distributed along a perforated pipe. Soak-aways are a possibility when the ground into which they are put is of a sandy or chalky nature, allowing the liquid to drain away rapidly; it is no use trying to employ a soak-away in heavy clay soil. To test the suitability of the soil, a porosity test should be carried out, which involves digging test pits and filling them with water. Based on how long it takes for these to empty, it is possible to calculate the permeability of the soil and, therefore, the size of soakaway needed.